The present invention relates to an artificial test soil for simulated use testing and cleaning validation studies of medical devices.
Proper reprocessing, which includes cleaning and/or disinfection/sterilization of medical devices is critical to ensure patient safety. The Association for the Advancement of Medical Instrumentation Technical Information Report (AAMI TIR #12, 1994), indicates that cleaning procedures and simulated use testing should be based on the type and quantity of contamination expected to be on the device after patient-use. Furthermore, the AAMI TIR goes on to indicate that xe2x80x9cthe soil selected should be that which most closely simulates the contamination and actual clinical usexe2x80x9d. In a draft guidance document (Nov. 5, 1998) produced by the Infection Control Devices Branch of the Food and Drug Administration (FDA), manufacturers are instructed to use xe2x80x9cworst case conditionsxe2x80x9d in their simulated-use testing. In addition, manufacturers are recommended to use an organic challenge xe2x80x9crepresentative of the types of soil to which devices are exposed during clinical usexe2x80x9d. The guidance document also recommends xe2x80x9c . . . that the bioburden challenge (organic and microbial) to the cleaning and/or disinfection process of the washer and washer-disinfectors be determined from clinically used devices.xe2x80x9d A draft guidance document for liquid chemical sterilants and high level disinfectants prepared by the FDA (Dec. 18, 1997) also provides simulated-use guidelines that have similar xe2x80x9cworst-casexe2x80x9d guidelines requiring an organic challenge xe2x80x9crepresentative of the type of organic load to which the device is exposed during actual use such as serum, blood, secretions etc.xe2x80x9d Despite these recommendations, there have been no publications that provide experimental data regarding the type and composition of soil (other than for viable bioburden determinations) that would be expected from medical devices.
Many test soils have been described and published for use in simulated-use testing, cleaning, high level disinfection, and sterilization validation studies. These published test soils include; Huckers soil, Edinburgh soil, various concentrations of whole blood, fibrin, a mixture of serum, dry milk powder, blood plus saline, and various concentrations of serum (AAMI TIR #12; 1994, Jacobs et al 1998, FDA December 1997, Verjat et al 1999). The wide range of test soils utilized by manufacturers and independent research groups have made it difficult to compare evaluations of the efficacy of sterilizers, and washer/disinfectors for reprocessing of medical devices. Likewise evaluations of cleaners or disinfectants are difficult to compare when the inorganic/organic test soil challenge is different. It would be a great value to have a standardized test soil that could be utilized by manufacturers as it would allow appropriate comparisons to be made between various studies.
Previous formulations of test soils including; Hucker""s soil, Edinburgh soil, various blood concentrations, fibrin, and various serum concentrations were not based on experimental data obtained from patient-used medical devices. Rather, they were based on common sense determinations. An example would be Hucker""s soil (AAMI TIR # 12), which contains lard, peanut butter, butter, flour, evaporated milk, egg yolk, ink, saline and dehydrated blood which was meant to simulate fecal material. The test soils comprised of various serum or blood concentrations were used since medical devices employed for surgery, or exposed to mucosal surfaces would be expected to be come in contact with such body substances. What is not known is the concentration of the various components such as protein, carbohydrate etc of such secretions that would be present.
The FDA recommendations and current guidelines by AAMI have recognized that xe2x80x9csimulated-usexe2x80x9d testing should include a representative inorganic/organic challenge. Otherwise testing by manufacturer""s will not mimic actual in-use conditions and could lead to approval of reprocessing methods that put patients at risk simply because the pre-testing was not challenging enough to identify potential problems. At the same time too harsh an inorganic/organic challenge is of little value, as all xe2x80x9csimulated-usexe2x80x9d testing would fail and potentially safe devices/processes would be unfairly prevented from being used.
The test soil formulations that have been published to date are not standardized and therefore, comparison of different studies is difficult as different test soil formulations were used. Because there has been no published data indicating what concentrations of the various soil parameters are present in secretions that patient-used medical devices are exposed to, there has been no basis for reaching a consensus regarding standardization of a test soil for xe2x80x9csimulated-usexe2x80x9d testing. The test soils that have been published to date have inappropriately high amounts of components such as hemoglobin or protein, yet lack other components such as bilirubin and endotoxin as shown herein. In addition, Jacobs et al (1998) have suggested that a ratio of protein to inorganic salts of about 10:1 is xe2x80x9c . . . not representative of the type of soils commonly found on surgical devices.xe2x80x9d This is shown herein not to be correct.
Currently there are no commercially available test kits that allow users to validate that adequate cleaning has been performed. The AAMI TIR #12 recommends xe2x80x9cAny test procedures that can be easily replicated in a health care facility and that can help user recognize whether or not cleaning was effective for all device surfaces should also be provided. Such tests are particularly important for devices with components that cannot be readily inspected for cleanliness (e.g. spring hinges, lumens, porous materials, crevices).xe2x80x9d Despite this recommendation, the availability of such tests is currently very limited. Cleaning validation is an integral part of an effective quality assurance program and staff competency validation. Despite recommendations by guidelines that indicate that Quality Assurance and staff training are critical parameters (Martin 1994, DiMarino et al 1996) for reprocessing of medical devices, no published or commercial methods exist for users to address these needs. There are a few published descriptions of cleaning validation tests based on residual protein (Kruger 1997, Verjat et al 1999, Roth et al 1999), however, no validation using patient-used devices has been included. In other words, the benchmark of what is an acceptable level of the test parameter was not determined experimentally and the cutoffs chosen in these reports were based on limits of detection of the test rather than actual in-use benchmark determinations. The cleaning validation method described by Roth et al (1999) does have benchmark data, but is based on radioactive tracer soil and as such is attuned to manufacturers and is not a test that could be adapted by users.
In view of the foregoing, there is a need in the art to provide test soil formulations that can effectively simulate soil levels from an actual clinical setting. There is also a need for cleaning validation kits to enable users to confirm that they have adequately cleaned a medical device.
The present invention provides an artificial test soil for simulated use testing and cleaning validation studies of medical devices. The artificial test soil (ATS) comprises: base medium, serum, blood and endotoxin. The artificial test soil may optionally contain bilirubin and/or mucin or carbohydrate.
In a preferred embodiment, the artificial test soil comprises: base medium, up to 20% v/v serum; up to 10% v/v blood; and up to 2,000,000 EU/ml endotoxin. If present, the bilirubin will be in the amount of about 1,000 nmoles/ml and the mucin or carbohydrate will be in the amount up to 10,000 xcexcg/ml.
The artificial test soil (ATS) can be used in many applications including (a) use by manufacturers to test equipment and cleaning and/or sterilization/disinfection compositions; (b) use by hospitals and other institutions to ensure adequacy of reprocessing; and (c) use to train staff in proper reprocessing procedures. In all these applications the ATS is used to evaluate the efficiency of a reprocessing method on a device. Accordingly, the present invention provides a method of evaluating a reprocessing method on a device comprising:
(a) applying an artificial test soil (ATS) comprising base medium, serum, blood and endotoxin to the device;
(b) subjecting the device to the reprocessing method to be evaluated; and
(c) determining the presence or absence of at least one contaminant on the device.
The ATS can also be used to evaluate the efficiency of a reprocessing method on the killing of microorganism(s).
Accordingly, the present invention provides a method of determining whether a reprocessing method can kill a microorganism on a device comprising:
(a) inoculating an artificial test soil (ATS) with a microorganism wherein the ATS comprises base medium, serum, blood and endotoxin;
(b) applying the inoculated ATS to the device;
(c) subjecting the device to the reprocessing method to be evaluated; and
(d) determining the presence or absence of the microorganism on the device.
The present invention also relates to a cleaning validation test kit comprising the artificial test soil of the invention and an indicator to determine if the contamination has been adequately removed from the medical device.
Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.